In standard communication devices using monaural audio reproduction systems, such as certain table radios, televisions, telephones, and speaker phones, all of the sound on the audio channel that is reproduced typically emanates from a single speaker. The listener is provided no sense of spatial separation between multiple sources of the various sounds emanating from the speaker. Stereo audio systems and more advanced surround sound audio systems, such as THX™, Dolby Pro Logic™, Dolby Digital™, DTS™, and Sony Dynamic Digital Sound (SDDS)™ add spatial aspects to the sound reproduction by virtue of the way in which the sound is split between two or more speakers (or channels) and/or audio processed (e.g., run through algorithms to alter the relative phases of the signals on the multiple output channels). This provides the listener with a more realistic sense of the location of the sources of the various sounds that might be reproduced. For instance, in a musical piece, the overall sound reproduction through a stereo system may give the sense that the singer is standing in the middle of the stage, the guitar player is standing on the right side of the stage, the bass player is standing on the left side of the stage, and the drummer is behind the singer. In fact, some of the audio processing algorithms available today can even provide a sense of sound coming from behind, above, or below the listener. Other techniques and algorithms are also able to simulate the sound of particular environments, such as a concert hall, a small room, or outdoors.
Overall, it is now possible to present a remarkably immersive and realistic audio experience using as few as two audio channels/speakers. The applications for such immersive three dimensional audio experiences are virtually limitless. To name just a few, they include, the audio accompanying television programs and movies, conference call systems, video games, and on-line virtual realities.